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• Aim: What are the Pythagorean Identities?

There are three Pythagorean Identities. Copy these down while you are watching the video.

Video

I thought this video was kind of cool. This shows how sine and cosine are related to the unit circle.

Video 2


Now that you know the the reciprocal identities, quotient identities, and the Pythagorean Identities, let's use them to simplify some trig expressions.

For each, write the given expression in terms of sine and cosine and express in simplest form.

1. (csc x)(sin x) 2. (sin x)(cot x) 3. (tan a)(cos a)

4. (sec a)(cot a) 5. sec x + tan x 6. (sec a)/(csc a)

7. (csc^2 x) - (cot x)/(tan x) 8. sce a (1 + cot a) - csc a (1 + tan a)

• Journal entry: Explain why the name Pythagorean Identity is appropriate.